1. Field of Invention
The present disclosure relates to light sources and, more particularly, to a fast switching arbitrary frequency light source for broadband spectroscopic applications.
2. Description of Related Art
Differential Absorption Light Detection and Ranging (DIAL) is a laser based method that may be used to measure and map concentrations and emissions of molecules in the atmosphere. The DIAL method may be performed by slow-switching lasers from a single on-resonance frequency to a single off-resonance frequency of the line of interest in the atmosphere.
The DIAL method is subject to drawbacks. For example, this method may be subject to retrieval errors in concentration because of the small number of spectral intervals measured across the line. This method may also be subject to retrieval errors because of changes in the atmosphere that may occur between the on- and off-resonance measurements.
There is a need for a laser-based method or device that enables retrieval of multiple points across the pressure broadened line of interest and that permits operation over time intervals much shorter than changes in the atmospheric conditions.
In order to perform cavity-enhanced or cavity ring-down measurements, some prior art methods and devices acquire lock of the light source to a mode of the cavity. These prior art methods and devices then perform signal averaging at that frequency, step the laser frequency and then reacquire lock for the next set of measurements.
However, these prior art methods and devices suffer from drawbacks in that it is difficult to maintain a single mode of operation of the laser during tuning. Also, a long period of time may be needed to reacquire a lock of the light source, and there is a lack of immunity to low frequency noise over the period of time needed to scan over the full line.
There is a need for a laser-based method or device that facilitates maintaining a single mode operation of the laser during tuning.
There is also a need for a laser-based method or device that overcomes difficulties associated with the time needed to reacquire lock of the light source. There is a need for a laser-based method that overcomes difficulties associated with lack of immunity to low frequency noise over the long period of time needed to scan over the full line.